1. Field of the Invention
The present invention relates to welding generators and inverters, and more particularly to an excitation circuit for brushless synchronous welding generators with an external pole exciter.
2. Description of the Prior Art
Presently known brushless synchronous welding generators are controlled by means of an externally supplied three-phase exciter having a stator-mounted excitation winding and a three-phase rotor winding with a series-connected rectifier. This known excitation control circuit has the shortcoming that, because of the dependency of the welding current from the adjusted idling voltage and because of the safety-related limitation of the idling voltage to a maximum of 100 volts, the machine must be so designed that, in order to assure a sufficiently high output in the upper region, the iron of the main machine is near its electrical saturation. It follows from this that the dynamic response of the machine in the area of maximum power output is poor, resulting in a large current-over-time integral, when short-circuited, and in a very slow voltage recovery, following opening of the short circuit.